A box of a truck, such as a pickup truck, is illustrated in FIG. 1. This box conventionally includes a horizontally enlarged floor or bed assembly 12 which extends sidewardly between and is joined to generally parallel and upwardly extending side panels or walls 13. The side panels 13 conventionally have wheelwell housings 14 formed therein, the latter typically projecting at least inwardly a small extent into the interior of the box. The front end of the floor assembly 12 is also rigidly joined to an upwardly projecting front wall or panel 15, the latter extending between and being rigidly fixed to the side panels 13. The rear of the box is normally closed by a rear panel 16, the latter conventionally being an openable tailgate 16 which is conventionally hingedly joined to the box and can swing into an open generally horizontal position wherein it is substantially flush with the floor assembly to provide access to the interior of the box.
This box, and specifically the floor or bed assembly 12, conventionally includes a horizontally enlarged main bed member 17, commonly referred to as the floor pan, which defines the actual floor of the box and extends lengthwise between the front and rear ends of the box, and has a width which normally substantially spans the width of the opening between the wheelwell housings. This main floor pan 17 is supported on a front cross rail 18, several intermediate cross rails 19, and a rear cross rail or sill member 21, the latter all extending transversely under the pan and being fixedly secured thereto, such as by spot welding. Some of these cross members, such as the front rail 18, the frontmost intermediate rail 19 and the rear sill 21 are typically fixedly secured to the vehicle frame (not shown) in a conventional manner.
The bed assembly 12 also normally includes secondary bed or floor pan members 22, the latter being positioned adjacent and fixedly joined to opposite longitudinal edges of the main floor pan 17 so as to occupy the regions of the bed disposed forwardly and rearwardly of the wheelwell housings 14.
In the pickup box as conventionally constructed, the main floor pan 17 is provided with stiffening ribs 23 which project upwardly from the pan, with a plurality of such ribs being generally uniformly sidewardly spaced apart across the width of the pan and extending longitudinally of the pan over a majority of the length thereof. These ribs, which are deformed upwardly from the pan to define a downwardly-opening channel-like cross section, generally extend rearwardly from the front free edge of the main pan 17 but the ribs normally terminate in tapered rib ends 24 which merge downwardly into the planar profile of the pan 17 at a location disposed close to but spaced forwardly a small distance from the rear free edge 25 of the pan. The rear edge portion of the main pan 17, namely the flat portion thereof which is free of the ribs, is then normally seated within a shallow recess formed in the top wall of the rear sill member 21 so as to be substantially flush with the upper surface of the sill member, with the rear pan and sill member then being suitably fixedly secured together, such as by spot welding. This arrangement enables the groovelike regions defined between adjacent ribs 23 to freely open outwardly through the rear end of the bed assembly, and hence prevent creation of pockets or recesses which would collect dirt or moisture.
A bed assembly having the structure described above has, for a very long time, been constructed using individual members which have been stamped utilizing large forming presses. That is, the main floor pan 17 as well as the cross rails 18, 19 and 21 have been conventionally formed from flat steel sheets by positioning a precut steel sheet in a forming press which deforms the sheet to define the desired cross section of the finished member. This stamping or press-forming technique, however, even though extensively utilized for many years, possesses recognized disadvantages which have nevertheless been long tolerated in view of the belief that this was the best manner of constructing the bed assembly.
More specifically, and particularly with respect to the main floor pan 17, the current and almost universally utilized technique of stamping the pan has resulted in limitations which have restricted optimum construction of the pan. For example, to stamp the main floor pan 17, a large rectangular sheet must be precut in accordance with the size of the desired pan being stamped. The sheet is initially of excess width so as to provide portions along opposite edges of the sheet which can be used for clamping the sheet and holding it in position when the sheet is positioned within the press and subjected to the stamping operation. Further, during the actual stamping operation, the material of the sheet is physically deformed by the stamping die so as to permit creation of the longitudinal ribs. This necessarily results in significant changes in thickness of the sheet material due to the deformation which is caused during the rib formation process. Not only does the sheet undergo significant changes in thickness, but this change in thickness is also of varying amounts at different locations across the rib, or through the cross section of the sheet containing the ribs, so that the resulting stamped floor pan has a sheet thickness which has significant variation therein. This thickness variation can in some instances be as much as 40% to 50%. This stamping process has also been observed to result in bends or corners which are inconsistent in terms of both material thickness and included angle, and have provided a finished exterior appearance which permits such irregularities to be visually observed. This stamping operation also requires, after the pan has been stamped, that the pan be subjected to a further stamping or cutting operation which is effective for removing the clamping strip portions on opposite sides of the sheet, which strip portions are disposed of as scrap.
In view of the inherent but inconsistent thickness reductions which occur during forming of the pan by the stamping or pressing process, the pan must also be initially formed from a sheet material of greater thickness than desired so as to compensate for the expected thickness reductions which occur during the stamping operation. This increases the overall weight of the pan. Further, in view of the significant size of the main floor pan and the fact that it is deformed or stamped in basically a single pressing operation, this also necessitates utilization of an extremely large and high-capacity forming press in order to accommodate both the size of the sheet and the significant pressing force encountered during the simultaneous deformation of the numerous ribs which extend longitudinally thereof. Further, these stamping operations necessarily can normally be successfully carried out only if lower strength and softer sheet steels are utilized since harder and higher strength steels will typically split or crack if subjected to severe deformation of the type encountered in the conventional pan stamping operation.
Accordingly, it is an object of this invention to provide an improved truck bed assembly, and a method of manufacturing and assembling the primary components of the truck bed assembly, so as to overcome many of the disadvantages associated with the conventional and long-utilized stamped bed assembly as described above.
More specifically, the present invention relates to an improved truck bed assembly, and process of manufacture, which involves formation of the floor pan by roll forming, with the floor pan having the strengthening ribs thereof extending longitudinally throughout the entire length of the floor pan so as to terminate at the front and rear edges thereof, with the rear edge of the floor pan cooperating with a rear sill member which is also preferably roll formed and has rib ends formed thereon and cooperating with the ends of the ribs on the main floor pan for closing off said ribs and creating a transition to a flat horizontal surface defined on the rear sill member. The rib ends on the rear sill member also preferably have portions which nest into and are fixedly secured to, as by spot welding, the rearward ends of the ribs defined on the main floor pan.
With the improved truck bed assembly and construction method of the present invention, as briefly summarized above, numerous constructional advantages are achieved in relationship to the conventional construction. More specifically, roll forming of the main floor pan permits utilization of higher strength sheet steel than is typically usable with stamping; roll forming permits the thickness of the formed pan to be substantially uniformly maintained throughout the entire cross section, thus eliminating the highly undesirable thickness variations created in the conventional stamping process, and hence enabling the pan to be formed from sheet steel of significantly smaller thickness, which reduction in thickness may be in the order of 30% to 40%; roll forming of the main floor pan permits creation of sharper corners or curvatures than is typically possible using a stamping operation; roll forming the main floor pan permits significantly higher consistency and uniformity in the rib structures including the corners than is possible using a stamping operation; roll forming of the pan provides better strength characteristics in the resultant product, and minimizes the creation of numerous high stress concentrations such as exists at the corners when the pan is stamped; roll forming of the pan enables the finished pan to be formed from sheet material which is originally of less width and in fact permits the pan to be formed from sheet material of a width which is all substantially used in forming the pan, whereas in contrast the stamping operation requires significantly wide edge portions which are clamped during the stamping operation and are then cut off and disposed of as scrap, such scrap edge portions not be necessary when the pan is roll formed; roll forming enables formation of the entire pan cross section including not only the strengthening ribs but also the securing flanges which project downwardly along opposite longitudinal edges of the main pan, whereas in contrast the stamped pan typically requires that the side flanges be formed separate from the main stamping operation, and in fact the stamping operation also often requires a restamping of the entire part so as to compensate for the spring back of the part created by the initial stamping operation; and roll forming of the pan and the ability to use thinner steel sheet and higher strength steel permits the overall weight of the pan assembly to be significantly reduced, such as by up to about 35%, thereby enabling reduction in the overall vehicle weight and hence improvement in fuel economy.
The present invention, in addition to the improvements and advantages briefly summarized above, is also believed to provide significant cost savings with respect to the overall manufacturing process, and permits creation of cross sections or shapes in the bed which is not possible with a stamping operation, including the creation of sharper corners having a higher consistency with respect to both curvature and thickness of bends.
Other objects and purposes of the invention will be apparent to persons familiar with structures and processes of this general type upon reading the following specification and inspecting the accompanying drawings.